Constant-Roll Inflationary Dynamics in Cosmology

Constant-roll inflationary dynamics represent a class of single-field models in which the usual slow-roll assumption is relaxed by requiring that the second slow-roll parameter remains constant throughout the inflationary epoch. This generalisation allows for analytical solutions beyond the standard quasi-de Sitter evolution, encompassing scenarios such as ultra slow-roll and models with large inflaton acceleration. By imposing a constant rate of change of the inflaton’s velocity, these models predict subtle deviations in the evolution of primordial perturbations, manifesting in specific imprints on the spectral index and the tensor-to-scalar ratio. The flexibility of the constant-roll framework has led to its extension into modified gravity, notably f(R) theories, where the constant-roll condition is formulated in the Jordan frame and translated into scalaron potentials in the Einstein frame. Investigations have also explored the interplay between constant-roll inflation and alternative thermodynamic formalisms, such as non-additive entropy approaches, pointing to potential connections with early dark energy dynamics. Constant-roll models offer a fertile ground for confronting theoretical constructs with high-precision observations of the cosmic microwave background and large-scale structure. They provide insights into the termination of inflation, the generation of non-Gaussian features and the possible unification of inflationary and post-inflationary eras. As observational constraints tighten, constant-roll dynamics stand as a versatile paradigm for probing the physics of the inflationary universe and its transition to the radiation-dominated era.

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Constant-Roll Inflationary Dynamics in Cosmology publication trend

The graph below shows the total number of articles in constant-roll inflationary dynamics in cosmology across all publications each year (not limited to Nature Index journals).

Technical terms

Constant-roll condition: A regime where the second slow-roll parameter remains constant during inflation, generalising the slow-roll approximation.

Inflaton: The scalar field posited to drive the rapid accelerated expansion in the early universe.

Slow-roll parameters (ε, η): Dimensionless quantities characterising the gradient and curvature of the inflaton potential, governing the dynamics of inflation.

Scalar spectral index (n_s): A parameter describing the scale dependence of primordial density perturbations.

Tensor-to-scalar ratio (r): The relative amplitude of primordial gravitational waves compared to scalar density fluctuations.

Tsallis entropy: A generalised non-additive entropy measure that modifies the statistical description of thermodynamic systems.

f(R) gravity: A class of modified gravitational theories in which the action is an arbitrary function of the Ricci scalar R, extending general relativity.

References

1. Constant-roll inflation field with Tsallis entopic proposal. European Physical Journal C (2023).
2. f(R) constant-roll inflation. European Physical Journal C (2017).
3. Ultra slow-roll inflation demystified. Physics Letters B (2017).
4. On the Constant-Roll Inflation with Large and Small ηH. Universe (2019).